The concentrated solar plant, built by Spanish firm Abengoa Solar, has been held up as a potential model for the future of solar power because it performs better in some ways than photovoltaic panels. Solana uses parabolic mirrors to focus the sun's rays on tubes containing a molten solution that retains high heat and powers two steam turbines. It can keep producing electricity for several hours after sunset, a much-touted feature that helps APS meet part of its late-afternoon peak load with renewable energy.

We checked on Solana's first-year output after reading an article last year about the unexpectedly dismal output of the Ivanpah concentrated solar plant in California. It turns out that plant, operated by NRG Energy Inc., is more sensitive to contrails and clouds than scientists realized and had produced only half of its expected output in its first year. After making some inquiries, New Times learned that the Solana plant's output was also under-whelming.

The Ivanpah concentrated solar plant in California has been plagued by problems that prevent it from producing anywhere near its expected output of electricity.

brightsourceenergy.com

Abengoa and APS, which is contracted with the Spanish company to buy the power Solana produces, told New Times in November that the plant was, in fact, working correctly. Although published reports and government documents about the plant all predicted its output would be about 900,000 megawatt-hours per year, and Solana had only produced 600,000 megawatt-hours in its first year, officials said the lower output was expected because time was needed to work out the kinks of the system.

Wait and see, they said — the numbers will go up.

According to Saturday's Wall Street Journal article by Cassandra Sweet, that might not be the case: "Ivanpah isn't the only new solar-thermal project is struggling to energize the grid. A large mirror-powered plant built in Arizona almost two years ago by Abengoa SA of Spain has also had its share of hiccups. Designed to deliver a million megawatt hours of power annually, the plant is putting out roughly half that, federal data show."

From that, it sounds like the plant's performance is getting even worse.

However, Brad Albert, APS' general manager of resource management, says he believes Solana's second year of production will exceed the first.

Projections show the second-year output will be "somewhere north of 700,000 megawatt-hours," Albert says.

A megawatt is equal to a million watts, and a megawatt-hour (mwh) of electricity is what's needed to keep, for example, 10,000 100-watt light bulbs burning for one hour.

Albert wasn't able to share Solana's output stats since January, saying he wasn't sure what the numbers were. But he admits it's possible the plant produced only half of its expected output for the first three months of 2015 due to maintenance work that interfered with plant operations.

Some of the steam-generation equipment was problematic last year, he says.

"That equipment had some leaks in it," he says. "That's why they had a maintenance outage — to address the problem that was the major holdup for them, if you will, last year."

He also points out that the WSJ erred in saying the plant was expected to produce one million megawatt-hours annually, so "half" of that higher figure actually would be more than half of the true expected output.

Albert also says he didn't have numbers today to show the plant had improved production from April to mid-June this year over the same time last year.

There's reason to think the plant must not have performed better since April compared to the previous year — namely, that awesome May we just had.

Dan Leins, a meteorologist with the National Weather Service in Phoenix, says that from April until now, there have been "more clouds across the entire region than what you'd have typically."

Sustained cloud cover can have a big impact on Solana's operation. Logically, then, the Solana plant is going to have to work much better than before if it's really going to get to 700,000 mwh for the year.

It already is working better, Albert says.

Despite the middling production from January to March due to maintenance, and despite the cloudy weather of the last couple of months, he's sticking with his projection of 700,000 mwh.

"The plant is gradually improving operations," he says, adding that Solana's cranking out the megawatts this week because of the sunny weather.

APS is only contracted to buy the electricity the plant produces, so its ratepayers won't lose money even if the plant habitually under-produces.

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Abengoa, which paid for the bulk of the plant's construction, stands to lose some of its investment if the plant never gets up to speed. (So do taxpayers, who chipped in 30 percent of the cost of construction.)

Concentrated solar plants have already been the source of criticism due to their high price compared to industrial-scale photovoltaic solar plants. Big projects like Solana and Ivanpah need to perform better if the public's going to help build more of them.

Frederick Redell, general manager for Abengoa Solar, sent New Times an email on Monday saying he was unable to comment for this article until sometime today. We'll update the article with his response after he contacts us.

Ray Stern has worked as a newspaper reporter in Arizona for more than two decades. He's won many awards for his reporting, including the Arizona Press Club's Don Bolles Award for Investigative Journalism.